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We conclude that both famotidine 10 mg and ranitidine 75 mg significantly raise intragastric pH when given as single post-prandial doses. Famotidine 10 mg may have a greater effect than ranitidine elixir 75 mg over the 5-9-h period after dosing.

Aim: To establish whether patients taking famotidine 10 mg to treat an episode of heartburn were protected from a recurrence of symptoms after a subsequent test meal. Methods: Frequent heartburn sufferers (n=366) were randomized to receive double blind treatment with famotidine 10 mg or 2×250 mg chewable alginate tablets within 30 min of a spontaneous episode of heartburn. After 4 h, patients with no or slight residual symptoms consumed a meal likely to induce heartburn. Over the next 4 h patients recorded the severity of heartburn and any consumption of ‘rescue’ antacids. At the end of this time they rated the global efficacy of their treatment in controlling meal‐induced symptoms. Results: Study groups were well matched for all baseline characteristics. Of the 366 randomized patients, 276 took study medication and data from 269 patients (132 famotidine, 137 alginate) were analysed for efficacy. Compared to the alginate control group famotidine treated patients reported better global efficacy following the test meal (P<0.001; relative odds for a more favourable response: 2.26 [95% CI: 1.45–3.53]). Fewer patients receiving famotidine resorted to antacid rescue (P = 0.038; relative odds for a more favourable response: 2.24 [95% CI: 1.04–4.79]) and peak heartburn was significantly less severe with famotidine treatment (P<0.001; relative odds for a more favourable response: 2.90 [95% CI: 1.85–4.53]). Eleven famotidine‐treated patients (8%) and 13 alginate patients (9%) reported adverse events. Conclusion: Compared to patients receiving an alginate preparation, patients self medicating with famotidine 10 mg for heartburn are better protected against a recurrence of their symptoms when they next eat. This suggests that the duration of acid control (9 h) previously demonstrated with this dose translates into a similar duration of measurable symptom control during the day.

To investigate the relative abilities of low doses of famotidine and cimetidine to raise intragastric pH after a single postprandial evening dose, 16 healthy volunteers were recruited to a four period crossover trial of famotidine 10 mg, cimetidine 100 mg and 200 mg compared with placebo. Intragastric pH was monitored between 1800 and 0730 with a nasogastric pH electrode. Median gastric pH rose from 1.35 (interquartile range 1-1-1-65) with placebo to 1 95 (1.6-5.35, p0.2) after cimetidine 100 mg. Intragastric pH was above 3 for 34% (p<0.005) of the time after dosing with famotidine, compared with 13.6% (p>0.2) after cimetidine 200 mg, 9.5% (p>02) after cimetidine 100 mg, and 4.7% after placebo. The rise of intragastric pH after famotidine 10 mg is significantly greater than that after either 200 mg or 100 mg cimetidine when the drugs are used postprandially. (Gut 1995; 37: 325-328) Keywords: H2 receptor antagonist, intragastric pH, famotidine, cimetidine. Study designThe investigation was designed as a four period crossover study with all subjects receiving the four different preparations in a random order. The study was partially blinded in that the drugs were recognisably different but the subjects were not aware of which was which. Of the two principal investigators one (RPW) was blinded to the drugs. There was a wash out period of at least six days between studies.On each study day subjects arrived at 1700 on the investigation unit having fasted for six hours. Bipolar glass pH electrodes (Ingold M440) were calibrated in standard buffer solutions of pH 7.00 and 4.01 and calibration was verified at pH 1.69. These electrodes were passed by the nasogastric route. A drop in pH to less than 2 was taken as evidence of the tip of the probe having entered the stomach, and the electrode was advanced a further 8 cm from this point. At 1830 a standard meal was given, which consisted of a supermarket ready meal of cottage pie, peas, and carrots, followed by chocolate coated ice cream and two chocolate mints to give a total of 700 kcal, provided by 22 g protein, 70 g carbohydrate, and 37 g fat, accompanied by 250 ml mineral water.

We used continuous variable rate infusions of famotidine in eight normal volunteers under fasting conditions to raise intragastric pH to 5-0. An intragastric glass electrode continuously monitored acidity and this information was automatically computed to regulate an intravenous infusion system (Gastrojet). The computer was programmed to aim for pH 6*0, increasing and lowering infusion rates accordingly. Two regimens were compared with placebo (10 mg bolus followed by infusion or infusion of famotidine alone). Volunteers were admitted to an investigation ward and each study was preceded by a standard normal meal. Hydration was maintained with intravenous fluids. During placebo treatment the median pH was 1-5 and the pH was <5-0 for 98% of the time. All volunteers responded to famotidine but dosage requirements varied (range 41 mg to 126 mg). The median pH rose to 6*5 when infusions of famotidine followed boluses and to 6-6 when infusions alone were used -the pH was <5-0 for 20% (Ingold M440, Switzerland). The pH recording system has previously been described and validated.' A target pH is programmed and infusion rates are adjusted upwards until this value is reached. Rates are then decreased at 28 minute intervals while pH remains at or above target, but are increased after four minutes if the pH falls below target. A mark is recorded in the machines memory every time the rate is increased or decreased. Preliminary studies with the equipment had suggested that a target pH one unit higher than that actually expected should be programmed in order to limit fluctuations around the target value itself. A full validation study has been published elsewhere.6 Thus, a target of 6-0 was chosen for these studies. Famotidine, 40 ml (4 mg/ml), or placebo (normal saline) was loaded into plastic infusion bags which fit into the machine. The infusion bags were weighed before and after each study day to check on total infusion volumes. VOLUNTEERSEight healthy students (five men) participated in the study. They had normal biochemical profiles and haematology before entry and none required regular medication of any sort. The mean age was 22 years (range 20-25 years), mean weight was 72 kg (59-93 kg), and two were smokers. Informed consent was given and the study approved by the Central Birmingham Health Authority ethics committee. PROCEDURESVolunteers attended the investigation unit at 12 30 and a standard lunch was supplied (soup and roll, lasagne and ratatouille, chocolate mousse, coffee and mint chocolates: JS Sainsbury). The menu, quantity, and time of lunch were the same on every study day. Cigarette smoking and alcohol were not allowed.